U.S. Treasury yields rose Friday ahead of Federal Reserve Chair Kevin Warsh’s Jackson Hole keynote at 1400 GMT, while Germany’s 10-year government bond yield climbed to 3.275%, its highest level since 2011 and a 15-year high, as European sovereign debt remained vulnerable to persistent inflation, hawkish central-bank guidance, elevated energy prices and heavy issuance. Investors sought clues on returning inflation to target, the impact of high long-term borrowing costs, the future policy path and the Fed’s response to rising fiscal pressures. Markets expected Warsh to avoid detailed forward guidance and emphasize broad themes. The European selloff intensified after ECB Executive Board member Isabel Schnabel said rates needed to rise further to return euro-area inflation to the 2% target, prompting markets to price an almost full probability of a 25-basis-point September ECB increase. European governments also face structural supply pressure from bond sales funding defense and energy-transition initiatives, while Treasury plans to at least double longer-dated note buybacks from $2 billion to at least $4 billion per operation from Sept. 9 through Nov. 4.